For the ferro rods you need to press quite firmly with the striker. You really are shaving bits of metal off an alloy rod.
A while back I did a group buy on some strikers and they really are good, but of course they're made for the purpose. All the edges have sharp corners. They're cheap enough.
http://www.bushcraftuk.com/forum/showthread.php?t=84583
Of the oddments from the workshop that I've tried as strikers I've found that the best is the broken edge of an all-hard high-speed steel blade. (They're the more expensive ones that are often painted blue, grey or green, but not the even more expensive bi-metal ones.) Because they're all hard they're rather brittle, and when they break the broken edges have very sharp corners. Not sharp as in razor blade, but sharp as in a 90 degree corner with virtually no rounding. Usually one of the broken edges is convex and the other concave, so I use the concave bit. You sometimes see large blades for machine hacksaws (an inch or more deep as opposed to about half an inch for a hand tool) and if you can get one of them it will make a good striker. The hacksaw blade pieces (usually blackened) that are supplied with many ferro rods aren't really up to much, the metal isn't as hard and the corners aren't usually really sharp.
People talk about using the spine of your knife. If you have a knife made, many makers will ask you if you want a spine with sharp corners. Otherwise, most knives have rather rounded corners on the spine. I can only think of two of my knives that have sharp spines. A spine with rounded corners is much more comfortable on the hands for things like push cuts than one with sharp corners, but it won't strike sparks well, if at all, from a ferro rod. I prefer a spine with rounded corners. I don't like using a knife for this purpose anyway, the sparks when you do get them are easily hot enough to melt little pits in steel. I usually have a couple of strikers of some sort stashed in my kit somewhere, or in a pocket.
